Posterio spinal device and method

ABSTRACT

An intervertebral joint assembly includes an upper support and a lower support, each of which has two or more components. The upper and lower support components are arranged in situ to form the upper and lower supports, respectively. By arranging the supports in situ, the supports can be introduced from the back of the patient, for example with an arthroscope. Each of the upper and lower supports has a surface adapted to engage a vertebra and a surface adapted to engage the other support or an intermediate member to form an articulate joint which articulates the joint assembly. In some embodiments, the components of the upper and lower supports are assembled in situ, for example with pivoting, telescoping or bending, to form the upper and lower supports, respectively. The supports can be attached to vertebrae with pedicles screws, and/or other anchors attached to the supports.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional of U.S. application Ser. No.12/025,561 filed Feb. 4, 2008, which application is a Continuation ofU.S. application Ser. No. 11/787,110 filed Apr. 12, 2007, which claimspriority from the following provisional applications: U.S. Appl. No.60/744,710 filed Apr. 12, 2006, entitled “Spinal Disk Arthroscopy”; U.S.Appl. No. 60/746,731 filed May 8, 2006, entitled “Spinal DiskArthroscopy”; and U.S. Appl. No. 60/883,493 filed on Jan. 4, 2007,entitled “Spinal Disk Arthroscopy”; the full disclosures of which areincorporated herein by reference.

The disclosure of the present application is related to those of U.S.application Ser. No. 10/855,253 filed May 26, 2004, entitled “ProstheticDisc for Intervertebral Insertion” (now U.S. Pat. No. 7,753,956); U.S.application Ser. No. 10/913,780 filed Aug. 6, 2004, entitled “Methodsand Apparatus for Intervertebral Disc Prosthesis Insertion” (now U.S.Pat. No. 7,585,326); U.S. Appl. No. 11/187,733 filed Jul. 21, 2005,entitled “Intervertebral Prosthesis Placement Instrument” (now U.S. Pat.No. 7,637,913); U.S. application Ser. No. 10/903,913 filed Jul. 30,2004, entitled “Intervertebral Prosthetic Disc with Metallic Core” (nowU.S. Pat. No. 7,575,599); U.S. Appl. No. 60/820,769 filed on Jul. 28,2006, entitled “Spinal Prosthesis with Offset Anchors”; U.S. Appl. No.60/820,770 filed on Jul. 28, 2006, entitled “Spinal Prosthesis withMultiple Pillar Anchors” the full disclosures of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to medical devices and methods. Morespecifically, the invention relates to a prosthetic disc forintervertebral insertion, such as in the lumbar and cervical spine. Theinvention also relates to the replacement of zygophyseal joints.

In the event of damage to a lumbar or cervical intervertebral disc, onepossible surgical treatment is to replace the damaged disc with anintervertebral disc prosthesis. Several types of intervertebral discprostheses are currently available. One type available under thetrademark LINK® SB Charite (Waldemar Link Gmbh, Hamburg, Germany),includes upper and lower prosthesis plates or shells which engage theadjacent vertebral bodies with a low friction core between the plates.[See EP 1142544A1 and EP 1250898A1] A potential drawback of that designis that the prosthetic device must be inserted from the anterior side ofthe patient, and this approach can be difficult and may require avascular surgeon as the prosthetic devices passes near important bloodvessels located anterior to the spine. Other currently availableintervertebral disc prostheses usually have similar drawbacks, includinginvasiveness of the surgery and/or surgical skill and complexity.

Another prosthetic approach has been to fuse the vertebrae, for examplewith transforaminal lumbar interbody fusion (TLIF) surgery or posteriorlumbar interbody fusion (PLIF) surgery. Fusion surgery generallyrequires at least partial removal of one or more facet joints, bonegrafting, and support with a fusion cage to stop the motion at thatsegment.

2. Description of the Background Art

Published U.S. patent applications 2002/0035400A1 and 2002/0128715A1describe disc implants which comprise opposing plates with a corebetween them over which the plates can slide. Other patents related tointervertebral disc prostheses include U.S. Pat. Nos. 4,759,766;4,863,477; 4,997,432; 5,035,716; 5,071,437; 5,370,697; 5,401,269;5,507,816; 5,534,030; 5,556,431; 5,674,296; 5,676,702; 5,702,450;5,824,094; 5,865,846; 5,989,291; 6,001,130; 6,022,376; 6,039,763;6,139,579; 6,156,067; 6,162,252; 6,315,797; 6,348,071; 6,368,350;6,416,551; 6,592,624; 6,607,558; 6,706,068 and 6,936,071. Other patentapplications related to intervertebral disc prostheses include U.S.Patent Application Publication Nos.: 2003/0009224; 2003/0074076;2003/0191536; 2003/0208271; 2003/0135277; 2003/0199982; 2001/0016773 and2003/0100951. Other related patents include WO 01/01893A1, WO2005/053580, EP 1344507, EP 1344506, EP 1250898, EP 1306064, EP 1344508,EP 1344493, EP 1417940, EP 1142544, and EP 0333990.

BRIEF SUMMARY OF THE INVENTION

The present invention provides an implanted intervertebral jointassembly which both restores motion and can be implanted from the backof the patient, thereby decreasing the invasiveness of the procedure,for example with a smaller posterior surgical incision avoidingimportant blood vessels located anterior to the spine.

In specific embodiments, the prosthesis is inserted into theintervertebral space from a posterior lateral approach. The posteriorlateral approach may substantially comprise a Wiltse approach. Tissuecan be dissected with a blunt instrument along the posterior lateralapproach. An access opening from about 7 to 15 mm across may be formedalong the posterior lateral approach. In many embodiments, the facetjoints of the adjacent vertebrae remain substantially intact afterinsertion of the prosthesis into the intervertebral space.

In specific embodiments, the spinal disc annulus is penetrated to formanother opening away from the opening. A distraction tool is insertedthrough the another opening to distract the adjacent vertebrae. Thevertebrae can be distracted with the distraction tool while theprosthesis is inserted through the opening.

In many embodiments, the expandable prosthesis can be removed from aremoval opening formed to remove the expandable prosthesis. In specificembodiments, the expandable prosthesis can be removed from an insertionopening formed to insert the expandable prosthesis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross sectional side view of an intervertebral jointassembly;

FIG. 2A shows an upper ring formed from arcuate sections;

FIG. 2B shows a lower ring formed from arcuate sections;

FIG. 2C shows a top down view of an upper ring formed with three arcuatesections and a low profile connector;

FIG. 2D shows a torsion stops formed in an upper ring;

FIG. 3 shows a cross-sectional side view of a joint assembly supportedwith screws;

FIG. 4 shows a top down view of the joint assembly of FIG. 3.

FIG. 5 shows a self expanding intervertebral joint assembly inaccordance with an embodiment.

FIGS. 6A-6D show a method for introducing the joint assembly of FIG. 5into an intervertebral space.

FIGS. 7A and 7B show the biconvex core of the joint assembly of FIGS. 5and 6A-6D.

FIGS. 8A-8E show the distal support component of the upper support ofFIGS. 5 and 6A-6D.

FIGS. 9A-9C show the middle support component of the upper support ofFIGS. 5 and 6A-6D.

FIGS. 10A-10D show the proximal support component of the upper supportof FIGS. 5 and 6A-6D.

FIGS. 11A-11D show the distal support component of the lower support ofFIGS. 5 and 6A-6D.

FIGS. 12A-12D show the middle support component of the lower support ofFIGS. 5 and 6A-6D.

FIGS. 13A-13D show the proximal support component of the lower supportof FIGS. 5 and 6A-6D.

FIG. 14 shows an embodiment using anchoring screws driven from theposterior instead of elongate anchors.

FIGS. 15A to 15D show a method of implanting a self expandingintervertebral joint assembly as in FIG. 14 according to an embodiment.

FIG. 16 shows a self expanding intervertebral joint assembly with acurved proximal component a curved middle component according to anembodiment.

FIG. 17 shows a perspective view of a self expanding intervertebraljoint assembly with gears in accordance with embodiments of the presentinvention.

FIG. 18 shows a schematic illustration of a placement instrument with acartridge loaded with a self-expanding intervertebral joint assembly asin FIG. 17 in accordance with embodiments of the present invention.

FIGS. 19A and 19B schematically illustrate details of the self-expandingintervertebral joint assembly loaded in the cartridge as in FIGS. 17 and18, in accordance with embodiments of the present invention.

FIGS. 20A to 20E show a method for introducing the joint assembly withthe cartridge as in FIGS. 17 to 19 into an intervertebral space, inaccordance with embodiments of the present invention.

FIGS. 21A to 21D show posterior lateral access to the intervertebralspace, according to embodiments of the present invention.

FIGS. 22A to 22E show a method for introducing a joint assembly into anintervertebral disc space, in accordance with embodiments of the presentinvention.

FIGS. 23A and 23B show radiopaque markers on upper and lower supports ofan expandable intervertebral prosthesis, according to embodiments of thepresent invention.

FIGS. 24A to 24E show a method of removing an expandable intervertebralprosthesis as in FIGS. 20A to 20E, in accordance with embodiments of thepresent invention.

FIGS. 25A to 25D show blunt dissection of tissue to access theintervertebral space, according to embodiments of the present invention.

FIG. 26 shows an expandable intervertebral prosthesis comprising anupper support that engages a lower support to articulate, according toembodiments of the present invention.

FIG. 27 shows self expanding prostheses that can be stacked in adjacentintervertebral spaces, according to embodiments of the presentinvention.

FIGS. 27A to 27C show in situ deployment of an expandable articulateintervertebral prosthesis in an intervertebral space with a placementinstrument and a contralateral placement instrument, according toembodiments of the present invention.

FIGS. 28A to 28D show a placement instrument as in FIGS. 27A to 27C,according to embodiments of the present invention.

FIGS. 29A to 29D show a contralateral placement instrument as in FIGS.27A to 27C, according to embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is generally directed to replacement of spinaldisc and zygophyseal joints, for example joints between facets ofinferior and superior articular processes of adjacent vertebra. Byproviding components which can be assembled in situ to form supports,the surgical site can be accessed from the back or posterior side of thepatient. This access to the surgical site from the posterior side of thepatient can be easier to perform. For example where access to thesurgical site avoids important arteries and/or veins, the presence of avascular surgeon may not be necessary.

The present invention provides an implanted intervertebral jointassembly which both restores motion and can be implanted from the backof the patient, thereby decreasing the invasiveness of the procedure,for example with a smaller posterior surgical incision avoidingimportant blood vessels located anterior to the spine. Components of theassembly are usually introduced to the surgical site through anincision, in some instances aided with an arthroscope (or other viewingdevice), and assembled in situ to form an upper support and a lowersupport. Each of upper and lower supports has a surface adapted toengage a vertebra and a surface adapted to engage the other support oran intermediate member to form an articulate joint which articulates thesupports. The upper and lower supports usually include bone anchorsand/or structures to receive anchoring screws to anchor the supports tothe vertebrae. The intervertebral joint assembly with formed supports isimplanted between vertebrae to replace a damaged disc or damagedzygophyseal joint, thereby providing an articulate prosthesis at theimplant site.

The components can be assembled, formed and arranged in many ways toform the supports in situ. For example, the upper and lower supports canbe formed by injecting a bladder with a polymer or by deformation of ametal as with stents. Typically, the upper and lower supports will beshaped as rings, discs, triangles, polygons or the like, and thecomponents will be a segment or portion of the support so that assemblyof the components forms the support. For example, in the case of rings,the components may each be an arc of the ring, with no one arc spanningmore than 180 degrees. Thus, there will be at least two ring components,more often at least three or more ring segments. The segments may bejoined in a variety of ways. In the illustrated embodiments shown below,the segments are joined by pivots, but in other embodiments thecomponents could be joined by springs, fasteners, coaxial (telescoping)sleeves, linkages, or the like. In still other embodiments, thecomponents could be unjoined prior to implantation and joined bycoupling members, screws, adhesives, or in other ways after introductioninto the patient.

In one aspect the present invention comprises an intervertebral jointassembly comprising an upper support and a lower support. The supportseach have two or more components which can be arranged in situ to formthe supports, so that the invasiveness of the surgery is minimized. Theupper support has a lower surface and the lower support has an uppersurface. The upper and lower surfaces are adapted to engage each otheror an intermediate member to form an articulate joint, thereby restoringat least some motion between vertebrae when the assembly is positionedbetween vertebrae. Although the intermediate member often comprisesbiconvex spherical surfaces, any combination of surfaces can be usedincluding plano/concave, plano/convex and biconcave surfaces. While themember is preferably made of metal such as cobalt chrome, the member canbe made of biocompatible polymer. For embodiments without anintermediate member in which the upper and lower surfaces of thesupports directly engage each other, the engagement surfaces aretypically concave and convex, and while the surfaces are preferablyformed in metal such as cobalt chrome, the surfaces can be formed in anybiocompatible material, for example polymer.

The supports will have surfaces adapted to engage the adjacent vertebraeand facilitate insertion of the assembly into the intervertebral space.Usually, the surfaces will be flat, although they may be modified orslightly shaped to conform to the vertebrae. In the illustratedembodiments, the two or more components will assemble to form an upperflat surface to engage an upper vertebra. Similarly, the two or morecomponents of the lower support will assemble to form a lower flatsurface to engage the upper surface of a lower vertebra.

In some embodiments, the vertebrae engagement surfaces may have anchorsand/or other structures to attach and anchor the supports to thevertebrae. For example, at least one component of the upper supportincludes at least one structure which is adapted to anchor the supportin an upper vertebra, for example an anchor or hole adapted to receivean anchoring screw; and/or at least one component of the lower supportincludes at least one structure which is adapted to anchor the supportin a lower vertebrae, for example an anchor or hole adapted to receivean anchoring screw. Various sizes and shapes of anchors can be used. Forexample, the anchor(s) can comprise an elongate anchor, or fin, adaptedto enter a groove formed in a vertebra while the assembly is insertedinto an intervertebral location. Also, the anchor may comprise aprotrusion having a tip adapted to engage the surface of the vertebrae,for a example a tip at the end of a pyramidal protrusion or a tip at theend of a conic protrusion. Additional anchors can be attached to each ofthe components. For example, at least two components of the uppersupport can comprise one or more anchors adapted to anchor the uppersupport in the upper vertebrae and/or at least two components of thelower support can comprise one or more anchors adapted to anchor thelower support in the lower vertebrae. Alternatively or in addition toanchors, at least one of the support components can include a structure,for example a hole, adapted to receive an anchoring screw. Anchoringscrews can be used instead of elongate anchors to attach the supports tothe vertebrae. For example, the use of anchoring screws can permitadjustment to the position of the joint assembly after the jointassembly is inserted in the intervertebral space because the screws canbe attached after the joint assembly is positioned at the desired finalposition within the intervertebral space.

Any number of appropriately arranged components can be assembled to formthe supports. For example, each support can comprise three or morecomponents with each component having a first end and a second end whichmechanically couple the components arranged to form the supports. Toprovide stability to the assembly, the engagement surfaces of thearticulate joint can be located at least partially within a bounded areaon each support defined by locations where the components are coupled,for example a triangular bounded area defined by three joints locatednear the ends of three interlocking components.

In the illustrated embodiments, the components of the supports arepivotally attached (hinged) so that they can be assembled in situ toform the support by unfolding the components at a surgical site. Forexample, the components can be adapted to fold or collapse to a narrowprofile, usually straight, configured for introduction to a surgicalsite. After introduction, the structure can be pivoted and/or unfoldedto form the first support at the surgical site. This process can berepeated to form the second support at the surgical site. In anotherembodiment, both supports are unfolded simultaneously. Such an“elongate” arrangement of components allows a smaller incision to beused, and in some instances allows the implant to be introduced with anarthroscope or other viewing devices. While assembly of the componentsto form the supports can be accomplished in many ways, assembly of thecomponents can include at least one of pivoting, telescoping or bendingthe components. In an embodiment, one or more supports comprise threecomponents: a distal component, a middle component and a proximalcomponent, and at least one of the three components includes an elongateanchor adapted to enter a groove formed in a vertebra. Alternatively, atleast one of the three components includes a hole to receive ananchoring screw.

Articulation of the upper and lower supports can be achieved in anynumber of ways. For example, the lower surface of the upper support cancomprise a convex or concave feature, and the upper surface of the lowersupport can comprise a concave or convex feature which mates the featureon the upper support. Alternatively, an intermediate member comprisingfirst and second curved surfaces, or a first curved surface and a secondflat surface, can be positioned between the supports so that the firstand second surfaces engage the upper and lower supports, respectively.Preferably, the intermediate member is allowed to move freely, or float,between both surfaces of the two supports. Alternatively, theintermediate member can be held rigidly against one of the supportswhile allowed to slide along the other support to articulate thesupports.

In many embodiments the upper support comprises an upper support ringand a lower support comprises a lower support ring, usually including anouter circular periphery and an open interior. The upper ring caninclude two or more separable components. The upper ring components canbe introduced in a disassembled condition and joined in situ to form theupper ring. The lower ring can include two or more separable components.The lower ring components can be introduced in a disassembledconfiguration and joined in situ to form the lower ring. The upper ringmay have a lower surface and the lower ring may have an upper surface.The upper and lower surfaces can be adapted to permit the rings toarticulate.

In some embodiments the lower surface of the upper ring may include aconvex or concave feature, and the upper surface of the lower ring mayinclude a concave or convex feature which mates the feature on the upperring. In further embodiments the upper and lower rings can separate intoat least two arcuate sections. In other embodiments, the upper and lowerrings can separate into at least three arcuate sections. In yet otherembodiments bone anchors may hold the rings in place. For example,external posts having elongate shafts can be used to attach the rings tothe bone anchors, and the elongate shafts can mate with the bone anchorsand/or the rings.

In another aspect the present invention comprises a method forintroducing a joint assembly to an intervertebral space between a pairof vertebral bodies. The upper support components are introduced. Theupper components are arranged in situ into an upper support. The lowersupport components are introduced to the intervertebral space. The lowersupport components are arranged into a lower support. The supportsurfaces are arranged to articulate.

In some embodiments the support components are introduced from the backof the patient (i.e. posteriorly). The upper support and/or the lowersupport can be attached to bone anchors to provide additional support,and external posts can be used to attach the bone anchors to the uppersupport and/or the lower support. The components of the upper and lowersupports can be introduced and arranged together. The components of eachsupport can be arranged by pivoting one or more components on eachsupport from a first narrow profile arrangement to a second wide profilearrangement. For example, at least one gear one each support can berotated to pivot the one or more components of each support.

In many embodiments a method for assembling an intervertebral prosthesisin situ within a patient comprises introducing components of theintervertebral prosthesis into the patient in a narrow profilearrangement. The components at least one gear is rotated to pivot thecomponents from the narrow profile arrangement to a wide profilearrangement to assemble the prosthesis.

In specific embodiments, the components of the prosthesis are retainedby a placement instrument while the components are introduced in thenarrow profile configuration. The at least one gear can be disposed onone or more of the components and engaged by a rack disposed on theplacement instrument so that the at least one gear rotates while thecomponents are advanced distally and/or the rack is retractedproximally.

In another aspect, the present invention provides an instrument forintroducing a joint assembly to an intervertebral space between a pairof vertebral bodies. The instrument comprises a shaft and a cartridge toretain the joint assembly. The cartridge is coupled to the shaft. Thecartridge comprises a structure to engage the intervertebral jointassembly and pivot at least one component of the intervertebral jointassembly.

In specific embodiments, the structure comprises at least one of a rackor a gear to engage the intervertebral joint assembly. The cartridgecomprises a casing. The casing can be shaped to at least partially coverthe joint assembly and permit the joint assembly to slide relative tothe casing. The casing can be shaped to hold upper and lower componentsof the joint assembly together and limit movement while the casing atleast partially covers the joint assembly. The cartridge can comprise aninner part shaped to fit at least partially within the casing and moverelative to the casing. The shaft can comprise threads to advance theinner part and/or retract the casing. The inner part can comprise aprotrusion to extend between components of upper and lower supportcomponents of the joint assembly and limit movement. The protrusion cancomprise a wedge with proximally inclined opposing surfaces and opposedflanges to limit movement between upper and lower support components ofthe joint assembly.

In many embodiments an intervertebral joint assembly comprises an uppersupport having a lower surface in which the upper support comprises twoor more components and at least one gear to arrange the components. Theupper support components may be arranged in situ with rotation of the atleast one gear on the upper support to form the upper support. A lowersupport has an upper surface and comprises two or more components and atleast one gear to arrange the components. The lower support componentsmay be arranged in situ with rotation of the at least one gear on thelower support to assemble the lower support. The upper and lowersurfaces are adapted to engage each other or an intermediate member toform an articulate joint.

In specific embodiments, the at least one gear on each support can beconnected to the at least one of the components of each support so thatrotation of the at least one gear pivots the at least one component. Theat least one gear on each support can be fixed to the at least onecomponent. Each support can comprise three or more components and atleast two gears to arrange the three or more components. The two or morecomponents of each support can be connected with a joint, and rotationof the at least one gear on each support may pivot at least one of thetwo or more components about the joint. An axis of rotation of the atleast one joint can be aligned with an axis of rotation of the at leastone gear. Each surface may be formed in a protrusion extending from eachsupport. The at least one gear on each support may comprise an annularshape disposed around the protrusion on each support. Each protrusionmay comprise a flange that extends toward the intermediate member toretain the member. In addition or in combination, each protrusion maycomprise a retention element that extends at least partially over the atleast one gear to retain the at least one gear while the gear rotatesaround the protrusion. Each protrusion can extend from the component oneach support to an annular rim, and at least one annular rim cancomprise a bevel to limit articulation between the upper support and thelower support to a pre-determined angle.

In many embodiments, an intervertebral prosthesis is provided. Theprosthesis comprises a first support adapted to expand from a narrowprofile to an expanded profile while in the intervertebral space. Asecond support is adapted to expand from a narrow profile to an expandedprofile while in the intervertebral space. The first and second supportsare adapted to engage each other or an intermediate member to articulatewhile in the expanded configurations.

In many embodiments, the prosthesis comprises anchors adapted to permitstacking with another prosthesis positioned in an adjacentintervertebral space. In specific embodiments, the first support and thesecond support articulate with at least one of a flexion/extension, alateral bending, an axial rotation or a lateral translation.

In another aspect, a method of articulating between adjacent vertebraeis provided. The method comprises inserting an intervertebral prosthesisinto an intervertebral space between the adjacent vertebrae. Theintervertebral prosthesis is expanded from a narrow profileconfiguration to an expanded configuration. The prosthesis articulatesthe vertebrae in the expanded configuration.

In specific embodiments, the prosthesis is inserted into theintervertebral space from a posterior lateral approach. The posteriorlateral approach may substantially comprise a Wiltse approach. Tissuecan be dissected with a blunt instrument along the posterior lateralapproach. An access opening from about 7 to 15 mm across may be formedalong the posterior lateral approach. In many embodiments, the facetjoints of the adjacent vertebrae remain substantially intact afterinsertion of the prosthesis into the intervertebral space.

In many embodiments, a method of articulating adjacent vertebrae isprovided. The method comprises penetrating a spinal disc annulus locatedbetween the adjacent vertebrae to form an opening in the spinal discannulus. A spinal prostheses can be inserted in a narrow profileconfiguration through the opening. The spinal prosthesis can be expandedinside the annulus from the narrow profile configuration to an expandedprofile configuration. The spinal prosthesis can articulate thevertebrae while in the expanded configuration.

In specific embodiments, the spinal disc annulus is penetrated to formanother opening away from the opening. A distraction tool is insertedthrough the another opening to distract the adjacent vertebrae. Thevertebrae can be distracted with the distraction tool while theprosthesis is inserted through the opening.

In many embodiments, a method of removing an expandable prosthesis froman intervertebral space is provided. The method comprises collapsing theexpandable prosthesis from an expanded configuration to a narrow profileconfiguration while the prosthesis is positioned in the intervertebralspace. The expandable prosthesis is removed from the intervertebralspace in the narrow profile configuration.

In many embodiments, the expandable prosthesis can be removed from aremoval opening formed to remove the expandable prosthesis. In specificembodiments, the expandable prosthesis can be removed from an insertionopening formed to insert the expandable prosthesis.

In many embodiments, a method of preparing an intervertebral space for aprosthesis is provided. The method comprises removing material from theintervertebral space. An expandable member is inserted into theintervertebral space to evaluate the intervertebral space.

In specific embodiments, additional material is removed in response tothe evaluated intervertebral space. The expandable member may compriseat least one of a balloon or a template.

In many embodiments, a method of positioning a prosthesis in anintervertebral space is provide. The method comprises inserting a firstinstrument through a first surgical opening to contact the prosthesis ata first location. A second instrument can be inserted through a secondsurgical opening to contact the prosthesis at a second location. Aposition of the prosthesis can be adjusted with the first instrument andthe second instrument.

In specific embodiments, the second surgical opening comprises acontra-lateral opening. The second instrument may be connected to theprosthesis.

In another aspect, a prosthesis assembly for insertion into anintervertebral space is provided. The prosthesis assembly comprises afirst end portion adapted to attach to a first instrument while theprosthesis assembly is positioned in an intervertebral space. A secondend portion is adapted to attach to a second instrument while theprosthesis assembly is positioned in the intervertebral space.

In specific embodiments, at least one of the first end portion or thesecond end portion comprises a spacer adapted for removal from theprosthesis. The prosthesis assembly may be expandable from a firstnarrow profile configuration to a second expanded configuration, and theprosthesis assembly may comprise a locking mechanism to lock componentsof the prosthesis assembly in the expanded configuration.

In many embodiments, an instrument for introducing a prosthesis into anintervertebral space between a pair of vertebral bodies is provided, theinstrument comprises a shaft. A structure is connected to the shaft nearthe end of the shaft. The structure can be adapted to retain the jointassembly while the joint assembly is advanced into the intervertebralspace such that components of the prosthesis pivot from a narrow profileconfiguration to an expanded profile configuration while the prosthesisis advanced into the intervertebral space.

In specific embodiments, the structure may comprise at least one ofcasing or a spacer to limit movement of the components while thecomponents pivot from the narrow profile configuration to the expandedprofile configuration. The structure may comprise a spacer attached tothe components of the prosthesis.

FIG. 1 illustrates an intervertebral joint assembly 1 for insertion intoa spine 2 of a patient. The joint assembly can include an inferiorendplate 4 and a superior end plate 6. The joint assembly can beinserted between two adjacent spinal vertebrae, for example a superiorvertebra 8 and an inferior vertebra 10. Joint assembly 1 includes asuperior component such as an upper ring 14 and an inferior componentsuch as a lower ring 16. Upper ring 14 can be formed from separablecomponents 18 by joining separable components 18 in situ. Lower ring 16can be formed from separable components 20 in situ. In situ formation ofupper and lower rings 14 and 16 generally includes forming the ring withat least a portion of the ring between superior vertebra 8 and inferiorvertebra 10. Separable components 20 can be joined with a lockingmechanism 36. The locking mechanism includes a first interlockingsegment, such as channel 32, and second interlocking segment, such askey 34, generally in the appearance of a lock and key mechanism. Upperring 14 can include superior plate 6, and lower ring 16 can includeinferior plate 4. The end plates can attach the rings to the vertebraewith fins and or serrations as described in U.S. application Ser. No.10/855,253, filed May 26, 2004, entitled “Prosthetic Disc forIntervertebral Insertion”, U.S. Pub. No. 20050021145, the fulldisclosure of which has been previously incorporated herein byreference. Upper ring 14 has a lower surface 22, and lower ring 16 hasan upper surface 24 Lower surface 22 is formed with a feature such asradius of curvature 26. Upper surface 24 is formed with the feature suchas radius of curvature 26 so that the upper and lower surfaces mate. Forexample, as both the upper surface 24 and the lower surface 22 areformed to a spherical shape having radius of curvature 26, the surfacesmate and move along a spherical surface of articulation 28. Thespherical surface of articulation has a center 30. As shown in FIG. 1.the center of the surface of articulation is located in the inferiorvertebra 10, and upper surface 24 is convex while lower surface 22 isconcave. In an alternate embodiment, center 30 of surface ofarticulation 28 can be located in the superior vertebra 8, and uppersurface 24 concave while lower surface 22 is convex. In alternateembodiments, the upper and lower surfaces can be formed with a matingfeature which is not the surface of a sphere, such as an outer surfaceof a doughnut, or torus. Lower ring 16 can include a lower flange 40which limits motion of the rings over the surface of articulation. Aportion 48 of upper ring 14 can be formed to receive lower flange 40formed in lower ring 16, thereby limiting motion of the upper and lowerrings. Upper ring 18 can include an upper flange 42 which limits motionof the rings over the surface of articulation. A portion 50 of lowerring 16 can be formed to receive upper flange 42, thereby limitingmotion of the upper and lower rings. The components of the jointassembly can be made from any suitable biocompatible material includingTitanium, Cobalt Chrome. In particular, it may be desirable to coat aCobalt/Chrome surface with Titanium where the plates meet with thevertebrae. Also, it may be desirable to provide channels permittinglubrication of the convex and concave surfaces. Channels permittinglubrication of surfaces are described in U.S. application Ser. No.10/903,913, filed Jul. 30, 2004, entitled “Intervertebral ProstheticDisc with Metallic Core”, published under U.S. Publ. No. 2006/0025862,the full disclosure of which has been previously incorporated herein byreference.

Turning now to FIG. 2A, upper ring 14 can be formed with separablecomponents 18 such as arcuate sections 60 and 62. Locking mechanism 36can be used at two locations to permit the arcuate sections to be joinedtogether in situ to form the upper ring.

Turning now to FIG. 2B, lower ring 16 can be formed with separablecomponents 20 such as arcuate sections 66 and 68. Locking mechanism 36can be used at two locations to permit the arcuate sections to be joinedtogether in situ to form the lower ring.

Turning now to an embodiment illustrated in FIG. 2C, an upper ring 16can be formed with three arcuate sections 90, 92 and 94. Lockingmechanism 36 rigidly joins components 92 and 94. A first low profileconnector 82 joins arcuate section 90 and arcuate section 92. Lowprofile connector 82 can be formed in arcuate section 90. Arcuatesection 92 can have an opening formed thereon to receive low profileconnector 82, so as to permit insertion of low profile connector 82 intoarcuate connector 92. In alternate embodiments, arcuate section 90 canhave an opening formed thereon to receive low profile connector 82. Asecond low profile connector 84 joins arcuate section 90 and arcuatesection 94. Second low profile connector 84 can be formed in arcuatesection 90. Arcuate section 94 can have an opening formed thereon toreceive second low profile connector 84, so as to permit insertion oflow profile connector 84 into second arcuate connector 94. Insertion offirst low profile connector 82 into first arcuate section 92 andinsertion of second low profile connector 84 into second arcuate section94 forms upper ring 18 as a rigid structure. Lower ring 16 can be formedfrom three arcuate sections 20 in a manner similar to that shown abovewith respect to upper ring 14.

Turning now to FIG. 2D which shows torsion stops which can be providedto prevent torsional rotation of upper ring 14 relative to lower ring16. Stops 96 can be formed in the surface of upper ring 14. Lower ring16 can have openings 98 shaped to receive stops 96. Torsional motion islimited by stops 96 engaging the surface of lower ring 16. In alternateembodiments, stops can be formed in the surface of lower ring 16 andopenings can be formed upper ring 14 to receive the stops.

Turning now to FIG. 3, a cross-sectional side view of a joint assemblysupported with screws is shown. An inferior pedicle screw 100 isinserted into an inferior pedicle of inferior vertebra 10. Pedicle screw100 can comprise a conventional pedicle screw. Inferior pedicle screw100 supports lower ring 16 and anchors lower ring 16 to inferiorvertebra 10. A superior pedicle screw 102 is inserted into a superiorpedicle of superior vertebra 8. Superior pedicle screw 102 supportsupper ring 14 and anchors upper ring 14 to superior vertebra 8. Aninferior post 104 can be inserted from lower ring 16 into inferiorpedicle screw 100 to affix lower ring 16 to inferior pedicle screw 100.A superior post 106 can project upwards from upper ring 14 into superiorpedicle screw 102 to affix upper ring 14 to superior pedicle screw 102.In alternate embodiments, the pedicle screws or custom designed screwscan pass through support structures attached to the upper and lowerrings. These support structures may resemble rods as used in pedicularscrew fixation systems or may be integral posts forming part of theposterior part of the endplates. A dorsal, back or posterior location onspine 2 is generally designated as back 204 of spine 2 of the patient. Aventral, front or anterior location on spine 2 is generally designatedas front 202 of spine 2 of the patient.

Turning now to FIG. 4, a top down view of the joint assembly of FIG. 3is shown. A second inferior pedicle screw 120 is inserted into inferiorvertebra 10 of spine 2 of the patient to anchor the lower ring. Bothfirst inferior pedicle screw 100 and second inferior pedicle screw 120can be inserted from the back of the patient.

Components of lower ring 16 as described above can be provided at thesurgical site by access from the posterior side of the patient. Accesscan be provided to permit in situ assembly of intervertebral joint 1,for example posterior access and assembly with an arthroscope. Lowerring 16 can be formed in situ as described above, and anchored to theinferior vertebra 10 with the pedicle screws. Components of upper ring14 as described above can be provided and assembled at the surgical sitewith access from the posterior side of the patient. A second superiorpedicle support screw similar to first superior pedicle support screw102 can be inserted into superior vertebra 8. Upper ring 14 can beassembled in situ and anchored to superior vertebra 8 as described aboveto form assembled intervertebral joint 1.

FIG. 5 shows a self expanding intervertebral joint assembly 300. Theassembly includes an upper support 302 and a lower support 304. Anintermediate member, or biconvex core 306 is positioned between theupper and lower supports to permit the upper and lower supports toarticulate. An elongate anchor 308, is located on the upper support andanchors the assembly into the upper vertebra. Another elongate anchor310 is located on the lower support and anchors the lower support intothe lower vertebral. The elongate anchors are adapted to enter a grooveformed in the vertebrae. Pyramidal anchors 312 are located on the uppersupport to anchor the upper support into the upper vertebra. Pyramidalanchors 314 are located on the lower support and anchor the lowersupport on the lower vertebra.

Upper support 302 includes a distal component 320, a proximal component322 and a middle component 324 which can be arranged in situ to form theupper support. Distal component 320 is connected to proximal component322 with an articulate joint 326. Proximal component 322 is connected tomiddle component 324 with a joint 328. These components are arranged insitu to form the lower support by articulating the upper supportcomponents about the joints. An aperture 340 is located in the distalcomponent 320. A cable can be passed through the aperture. The cable isused to arrange the components by pulling on the cable to pivot thecomponents into place as described more fully herein below.

Lower support 304 includes a distal component 330, a proximal component332 and a middle component 334 which can be arranged in situ to form thelower support. Distal component 330 is connected to proximal component332 with an articulate joint 336. Proximal component 332 is connected tomiddle component 334 with a joint 338. These components are arranged insitu to form the lower support by articulating the upper supportcomponents about the joints. An aperture 342 is located in the distalcomponent 320. A cable can be passed through the aperture. The cable isused to arrange the components by pulling on the cable to pivot thecomponents into place as described more fully herein below.

The upper and lower supports include features which permit the supportsto articulate and restore motion between the vertebrae. Upper support302 has a protruding structure 325 which has a concave surface featureformed therein, as shown below, which mates the upper surface ofbiconvex core 306. Lower support 304 has a protruding structure 335which has a concave surface feature formed therein, as shown below,which mates the lower surface of biconvex core 306. In an alternateembodiment, the features of the upper and lower support are in directcontact and mate to provide articulation. For example, the upper supportcan have a protrusion with a convex surface, and the lower support canhave a protrusion with a concave surface, in which the two surfaces mateto form a load bearing articulate joint.

FIGS. 6A-6D show a method for introducing the joint assembly of FIG. 5into an intervertebral space. As shown in these figures, the upper andlower supports are arranged and introduced together, although the upperand lower supports can be arranged sequentially. In a preferredembodiment, an insertion instrument removably attaches to the proximalcomponents and holds the components together as shown in FIGS. 6A-6D.While many instruments can be adapted to removably attach the proximalcomponents, one such instrument is described in U.S. application Ser.No. 11/187,733, filed Jul. 21, 2005, entitled “Intervertebral ProsthesisPlacement Instrument”, the full disclosure of which has been previouslyincorporated herein by reference

Referring to FIG. 6A, distal component 320 and proximal component 322 ofthe upper support 302 are arranged in an elongate configuration forintroduction to the surgical site. Middle component 324 is folded withina recess so that the upper support components have a slender profile forintroduction into the surgical site. Distal component 330 and proximalcomponent 332 of lower support 304 are similarly arranged in an elongateconfiguration with middle component 324 is folded within a recess sothat the lower support components have a slender profile.

Referring now to FIG. 6B, the components are shown in an intermediateconfiguration. The distal components 320, 330 are pivoted proximallywith respect to the proximal components. Distal component 320 haspivoted about joint 326 to form an acute angle between the distalcomponent and the proximal component. Cable 350 is used to pull uppersupport distal component 320 and pivot distal component 320 about joint326. A stop 364 limits pivoting motion of distal component 320 inrelation to proximal component 322. Cable 352 is used to pull lowersupport distal component 330 proximally and pivot distal component 330about joint 336. A stop 404 (shown in FIG. 6A) limits pivoting motion ofdistal component 330. A groove (shown below) can be provided in each ofthe upper and lower distal components so that the middle components willnot deploy until the distal components have reached the stops.

Referring now to FIG. 6C, the middle components 324, 334 of the upperand lower supports, respectively, pivot outward after the distalcomponents are arranged. Upper cable 350 is attached near the distal endof middle component 324 so that cable 350 pulls on middle component 324to pivot about joint 328. Similarly, lower cable 352 is attached nearthe distal end of middle component 334 so that cable 352 pulls on middlecomponent 334 to pivot about joint 328 to form an acute angle betweenthe proximal component and the middle component. The cables are pulleduntil the middle components reach a final position as shown in FIG. 6D.The cable can also be guided through upper proximal component 322 andlower proximal component 332 and from there into a tensioner which canbe part of the placement instrument which will facilitate pullingthereof.

Referring now to FIG. 6D, this top view shows middle component 324 in afinal position so that the upper support is fully formed. Stops can beprovided on each of the distal and middle components to limit pivotingmotion of the middle components about the proximal components. The upperand lower support are fully formed once the middle components pivot toreach the stops. Stops can be formed with a protrusion which slides in agroove as described more fully herein below. Once the upper and lowersupports are fully formed, the joint assembly is inserted into theintervertebral space. In a preferred embodiment, the joint assembly isinserted partially into the intervertebral space in a rigid wedgeconfiguration and then allowed to freely articulate, so as to limitstretching and promote ligamentotaxis, as described in co-pending U.S.application Ser. No. 10/913,780, filed Aug. 6, 2004 entitled “Methodsand Apparatus for Invertebral Disc Prosthesis Insertion”, the fulldisclosure of which has been previously incorporated herein byreference.

FIGS. 7A and 7B show biconvex core 306 of the joint assembly 300 ofFIGS. 5 and 6A-6D. FIG. 7A shows a side view of the core, and FIG. 7Bshows a top view of the core. Core 306 includes a groove 351 and anupper flange 353 and a lower flange 354. Groove 351 engages a flange onthe lower support, shown herein below, to retain core 306 within jointassembly 300, as described in U.S. application Ser. No. 10/855,253,filed May 26, 2004, entitled “Prosthetic Disc for IntervertebralInsertion”, U.S. Pub. No. 2005/0021145, the full disclosure of which isincorporated herein by reference. Core 306 includes an upper convexsurface 356 and a lower convex surface 358. These surfaces mate withsurfaces in the protrusions described above. Core 306 can be made fromany biocompatible material including known biocompatible polymers andmetals. In a preferred embodiment, core 306 is made from metal, forexample cobalt chrome, and includes at least one channel 359 to permitfluid to lubricate the load bearing surfaces of the core, as describedin U.S. application Ser. No. 10/903,913, filed Jul. 30, 2004, entitled“Intervertebral Prosthetic Disc with Metallic Core”, published as U.S.Pub. No. 2006/0025862, the full disclosure of which is incorporatedherein by reference. Although core 306 is shown as biconvex, the corecan be any shape and have any combination of surfaces includingplano/convex, plano/concave and biconcave surfaces. Core 306 includes achannel 351 formed around the periphery of the core. Channel 351 isformed in core 306 to define an upper rim flange 353 and a lower rimflange 355. Channel 351 receives a flange on the lower support to limitmotion of the core in relation to the lower support, for example toprevent the core from sliding off the concave surface of the lowersupport. In an alternate embodiment, both the upper support and thelower support have a flange which is received by channel 351 to preventthe supports from sliding off the core.

FIG. 8A through FIG. 8E show distal component 320 of upper support 302.FIG. 8B shows a front view of distal component 320 while FIG. 8A, FIG.8C and FIG. 8D show top, side and cross-sectional views, respectively ofdistal component 320. Distal component 320 has a proximal end 362, andalso includes an aperture 360 formed near proximal end 362. Aperture 360mates with proximal component 322 to form pivot joint 326. Severalpyramidal anchors 312 are formed on the surface of distal component 320and anchor the support to the upper vertebra. Distal component 320includes a distal region 365, which is shown in detail in FIG. 8E. Eachpyramidal anchor has a square base about 0.9 mm on each side and aheight of about 0.8 mm. As shown in FIG. 8A aperture 340 is formed indistal component 320 to pass cable 350 as described above. A recess 366is formed in distal component 320 to permit the middle component topivot toward distal end portion 365. Within recess 366 a groove 368 isformed in component 320 which receives a protrusion formed in the middlecomponent, described herein below.

FIG. 9A through FIG. 9C show middle support component 324 of uppersupport 302. FIG. 9B shows a front view of middle component 324 whileFIG. 9A shows a top view and FIG. 9C shows a side view. Middle component324 has an aperture 370 formed near the proximal end. Aperture 370 mateswith proximal component 322 to form pivot joint 328. An aperture 380formed in the distal end of middle component 324 has cable 350positioned therein as described above. Proximal advancing of cable 352pivots middle component 324 about joint 328. An upper protrusion 376 islocated near the distal end of middle component 324. A lower protrusion378 is also located near the distal end of middle component 324.Protrusion 378 slides in grove 368 of distal component 320 as describedabove. Middle component 324 includes protruding structure 325.Protruding structure 325 includes a concave surface feature 372 whichengages the biconvex core. Protruding structure 325 also includes abevel 374 which mates with flange formed on protruding structure 335 asdescribed herein below.

FIG. 10A through FIG. 10D show proximal support component 322 of uppersupport 302. FIG. 10B shows a front view of component 322 while FIGS.10A, 10C and 10D show top, side and cross-sectional views of component322, respectively. An aperture 392 is formed near the proximal end ofproximal component 322. Aperture 392 mates with middle component 324 toform pivot joint 328 as described above. Proximal component 322 includeselongate anchor 308, and pyramidal anchors 312 as described above. Anaperture 390 is formed near the distal end of proximal component 322.Aperture 390 mates with distal component 320 to form pivot joint 326 asdescribed above. Proximal component 322 includes a recess 394 which atleast partially encloses middle component 324 while the components arein an elongate configuration as described above. Within recess 394component 322 has a groove 398 formed therein. Groove 398 receives theprotrusion of the middle component as described above to permit themiddle component to pivot from within recess 394 as described above. Acutout 396 is formed in proximal component 322. Cutout 396 receivesprotruding structure 325 while middle component 324 is positioned withinrecess 394.

FIG. 11A through FIG. 11D show distal component 330 of lower support304. FIG. 11B shows a front view of distal component 330 while FIG. 11A,FIG. 11C and FIG. 11D show top, side and cross-sectional views,respectively of distal component 330. Distal component 330 has aproximal end 336, and also includes an aperture 400 formed near proximalend 336. Aperture 336 mates with proximal component 332 to form pivotjoint 336. Several pyramidal anchors 314 are formed on the surface ofdistal component 330 and anchor the support to the lower vertebra.Distal component 330 includes a distal end 402. Each pyramidal anchorhas a square base about 0.9 mm on each side and a height of about 0.8mm. As shown in FIG. 11A aperture 342 is formed in distal component 330to pass cable 352 as described above. A recess 406 is formed in distalcomponent 330 to permit the middle component to pivot toward distal end405. Within recess 406 a groove 408 is formed in component 330 whichreceives a protrusion formed in the middle component, described hereinbelow.

FIG. 12A through FIG. 12D show middle support component 334 of lowersupport 304. FIG. 12B shows a front view of middle component 334 whileFIG. 12A shows a top view and FIG. 12C shows a side view. Middlecomponent 334 has an aperture 410 formed near the proximal end. Aperture410 mates with proximal component 332 to form pivot joint 338. Anaperture 420 formed in the distal end of middle component 334 has cable352 positioned therein as described above. Proximal advancing of cable352 pivots middle component 334 about joint 338. An upper protrusion 416is located near the distal end of middle component 334. A lowerprotrusion 418 is also located near the distal end of middle component334. Protrusion 418 slides in grove 408 of distal component 330 asdescribed above. Middle component 334 includes protruding structure 335.Protruding structure 335 includes a concave surface feature 412 whichengages the biconvex core. Protruding structure 335 also includes aflange 424, or retaining ring, as shown in detail in FIG. 12D. Flange424 mates bevel 374 as described above. Flange 424 is slopped at anangle 428 to mate with bevel 374 while the upper and lower supports ofthe joint assembly are deflected at a maximum angle of about sixdegrees. A groove 426 extends around protruding structure 335. Grove 426mates with the flange on the biconvex core described above, therebyretaining the biconvex core between upper protruding structure 325 andlower protruding structure 335. In an alternate embodiment, the uppersupport also includes a groove and a flange which are similar to groove426 and flange 424, and the upper support grove and flange mate withupper rim flange 353 and channel 351 as described above. Thus, in thisalternate embodiment both the upper support and the lower supportinclude groves and flanges which mate with the core to prevent the upperand lower supports from sliding off the core.

FIGS. 13A-13D show the proximal support component of the lower supportof FIGS. 5 and 6A-6D. FIG. 13A through FIG. 13D show proximal supportcomponent 332 of lower support 304. FIG. 10B shows a front view ofcomponent 332 while FIGS. 13A, 13C and 13D show top, side andcross-sectional views of component 332, respectively. An aperture 432 isformed near the proximal end of proximal component 332. Aperture 432mates with middle component 334 to form pivot joint 338 as describedabove. Proximal component 332 includes elongate anchor 310, andpyramidal anchors 314 as described above. An aperture 430 is formed nearthe distal end of proximal component 332. Aperture 430 mates with distalcomponent 330 to form pivot joint 336 as described above. Proximalcomponent 332 includes a recess 434 which at least partially enclosesmiddle component 334 while the components are in an elongateconfiguration as described above. Within recess 434 component 332 has agroove 438 formed therein. Groove 438 receives the protrusion of themiddle component as described above to permit the middle component topivot from within recess 434 as described above. A cutout 436 is formedin proximal component 332. Cutout 436 receives protruding structure 335while middle component 334 is positioned within recess 434.

FIG. 14 shows an embodiment of an articulate intervertebral jointassembly 500 using anchoring screws 506, 508, 510, and 512 instead of apair of elongate anchors as described above. Joint assembly 500 is madewith many of the components as described above and can be assembled insitu by unfolding and/or pivoting the components as described above.Joint assembly 500 includes an upper support 502 and a lower support504. Upper support 502 includes a protruding structure 514 on theproximal component and a protruding structure 516 on the distalcomponent. Protruding structure 514 has a hole formed therein to receiveanchoring screw 510, and protruding structure 516 has a hole formedtherein to receive anchoring screw 512. Lower support 504 includes aprotruding structure 518 on the proximal component and a protrudingstructure 520 on the distal component. Lower support protrudingstructure 518 has a hole formed therein to receive anchoring screw 506,and protruding structure 520 has a hole formed therein to receiveanchoring screw 508.

While joint assembly 500 is assembled in situ similarly to jointassembly 300 as described above, the use of screws instead of elongatefins can provide advantages. After upper support 502 and lower support504 are assembled in situ, joint assembly 500 is fully inserted andpositioned in the intervertebral space. In some embodiments, jointassembly 500 is assembled at least partially in the intervertebral spaceby pivoting the components while a portion of at least one component ispositioned within the intervertebral space. The position of assembly 500is adjusted to a desired final position after assembly 500 has beenfully inserted into the intervertebral space. Such adjustment afterinsertion into the intervertebral space can be difficult with someembodiments using elongate anchors as described above. The anchoringscrews are inserted to hold the joint assembly in place at the desiredfinal position. The anchoring screws are driven from the posterior ofthe patient and attach to the vertebrae and/or pedicles as describedabove. As shown in FIG. 14 the anchoring screws are used instead of theelongate anchors shown above, although anchoring screws can be used inconjunction with elongate anchors in other embodiments.

FIGS. 15A to 15D show a method of introducing a self expandingintervertebral joint assembly 500 as in FIG. 14 according to anembodiment. Joint assembly 300 can be similarly introduced. Jointassembly 500 is introduced into a patient P as shown in FIG. 15A. Apatient reference system 570 includes a lateral patient direction L, aposterior patient direction P and a vertical patient direction V.Vertical patient direction V corresponds to vertical as the patient isstanding and also corresponds to an inferior to superior orientation onthe patient. An intervertebral space 560 is located adjacent theinferior vertebrae 10. For clarity only one vertebra several vertebraeas described above is shown. As shown in these figures, the upper andlower supports are arranged and introduced together, although the upperand lower supports can be arranged sequentially. An oblique direction580 is located between the lateral and posterior directions. Althoughthe joint assembly is introduced into the patient from a posteriordirection, the implant can be rotated in the oblique direction near thespine to enter the spine along oblique direction 580. In someembodiments the joint assembly is introduced from the lateral direction,for example from the side of the patient. Although lateral introductionfrom the side of the patient can require a greater surgical distancetraversed from the skin of the patient to the implant site, the tissuecut is typically muscle or other soft tissue such that the lateralimplantation can be less invasive than implantation from the posteriordirection.

Referring again to FIG. 15A, the distal component and the proximalcomponent of the upper support are arranged in an elongate configurationfor introduction to the surgical site as described above. The middlecomponent is folded within a recess so that the upper support componentshave a slender profile for introduction into the surgical site. Thedistal component and the proximal component of the lower support aresimilarly arranged in an elongate configuration with the middlecomponent folded within a recess so that the lower support componentshave a slender profile.

Referring now to FIG. 15B, the components are shown introduced intointervertebral space 560 in the elongate configuration. The distalcomponent is advanced at least partially into the intervertebral spacewhile the components remain in the elongate configuration.

Referring now to FIG. 15C, the components are shown in an intermediateconfiguration in the intervertebral space. The components have pivotedabout the joints while the implant is positioned at least partiallywithin the intervertebral space. The distal components are pivotedproximally with respect to the proximal components, and the distalcomponents have pivoted about the joints. Cables as described above areused to pull the distal components and pivot the distal components aboutthe joints. The stops as described above limit pivoting motion of thedistal components in relation to the proximal components.

Referring now to FIG. 15D, the middle components of the upper and lowersupports have been pivoted outward to the final position. The cables areattached near the distal end of middle components so that cables pull onthe middle components to pivot the middle components about the joints,as described above. The middle components pivot while the proximal anddistal components are positioned within the intervertebral space. Thecables are pulled until the middle components reach the final positionas shown in FIG. 15D. In some instances, it may be desirable to positionthe implant within the intervertebral space after the upper and lowersupports are formed. The upper and lower supports are anchored to thevertebrae with screws as described above.

FIG. 16. shows a self expanding intervertebral joint assembly 600 with acurved proximal component and a curved middle component according to anembodiment. Joint assembly 600 shows modifications to joint assembly 300shown above, and joint assembly 500 can be similarly modified. An uppersupport 602 includes a distal component 620, a proximal component 622and a middle component 624. The distal component is attached to theproximal component with an articulate joint 626. The proximal componentis attached to the middle component with a joint 628. Proximal component622 includes a curved edge 640. Curved edge 640 can correspond with anycurve, for example an arc formed with from a radius of a circle. Curvededge 640 permits the proximal component to have a larger surface areaoriented toward the vertebra. Additional anchors, for example pyramidalanchors, are provided on this larger surface area to attach to thevertebra. Middle component 624 also includes a curved edge which nestsin proximal component 622. The curved edge of middle component 624provides the middle component with a larger cross sectional width and alarger surface area than embodiments 300 and 500 shown above. The largercross sectional width is sufficiently wide so that at least a portion ofthe middle component remains within the proximal component while thesupport is formed and no hole is present in the upper surface of theformed upper support. The lower support is formed similar to the uppersupport with curved edges on the proximal and middle components so as toprovide a larger surface area on the lower support and a formed lowersupport without a hole in the middle. In alternate embodiments, themiddle components include several small anchors, for example pyramidalanchors, on the surfaces oriented toward the vertebrae. In additionalembodiments, the middle component is curved on the outer edge oppositeedge 640 so that the upper support is curved on each outward facing edgeof the proximal, distal and middle components. In these additionalembodiments, the lower support is similarly formed.

FIG. 17 shows a perspective view of a self expanding intervertebraljoint assembly 700 with gears in accordance with embodiments of thepresent invention. The assembly includes an upper support 702 and alower support 704. An intermediate member, or biconvex core 706 ispositioned between the upper and lower supports to permit the upper andlower supports to articulate. Pyramidal anchors 712 are located on theupper support to anchor the upper support into the upper vertebra.Pyramidal anchors 714 (shown in FIG. 19) are located on the lowersupport and anchor the lower support on the lower vertebra.

Upper support 702 includes a distal component 720, a proximal component722 and a middle component 724 which can be arranged in situ to form theupper support. At least one gear is disposed on each of the componentsof the upper support. Distal component 720 is connected to proximalcomponent 722 with an articulate joint 726. Proximal component 722 isconnected to middle component 724 with a joint 728. These components arearranged in situ to form the lower support by articulating the uppersupport components about the joints. A retention ring gear 716 islocated on the upper support and disposed around the protrudingretention ring structure of the upper support that retains the biconvexcore as described above. In many embodiments, gear 716 may comprise afreewheeling gear. Gear 716 can be used to arrange the components of theupper support by rotating so as to pivot the components into place asdescribed more fully herein below.

Lower support 704 includes a distal component 730, a proximal component732 and a middle component 734, which can be arranged in situ to formthe lower support. At least one gear is disposed on each of thecomponents of the lower support. Distal component 730 is connected toproximal component 732 with an articulate joint 736 (shown below in FIG.19). Proximal component 732 is connected to middle component 734 with ajoint 738 (shown below in FIG. 19). These components are arranged insitu to form the lower support by articulating the upper supportcomponents about the joints. A retention ring gear 718 is located on thelower support and disposed around the protruding retention ringstructure of the lower support that retains the biconvex core asdescribed above. In many embodiments, gear 716 may comprise afreewheeling gear. Gear 718 can be used to arrange the components of thelower support by rotating so as to pivot the components into place asdescribed more fully herein below.

FIG. 18 shows a schematic illustration of a placement instrument 800with a cartridge 810 loaded with a self-expanding intervertebral jointassembly 700 as in FIG. 17 in accordance with embodiments of the presentinvention. The cartridge can permit smooth deployment of theintervertebral joint assembly in a narrow, uneven space such as a narrowuneven intervertebral space. Cartridge 810 comprises an outer cartridgecasing 820, an inner cartridge part 830, and a shaft 840. Shaft 840 isconnected to cartridge 810. Shaft 840 has threads 842 formed thereon.Threads 842 mate with threads 822 formed in outer cartridge casing 820.A knob 844 is connected near one end of shaft 840 and rotation of knob844 causes rotation of shaft 840 so as to advance shaft 840 in relationto outer cartridge casing 820.

Rotation of shaft 840 can advance inner cartridge part 840 so as toadvance and deploy self-expanding intervertebral joint assembly 700.Shaft 840 is connected to inner cartridge part 830 such that rotation ofshaft 840 can cause inner cartridge part 830 to advance distally alongwith shaft 840. Self expanding intervertebral joint assembly 700 ispositioned near inner cartridge part 830. As inner cartridge part 830advances distally intervertebral joint assembly 700 is pushed forwardand advances distally. In some embodiments outer cartridge casing 820can retract while the inner cartridge part advances distally or retractwhile the inner remains, The gears of the intervertebral joint assemblyare mechanically coupled to the outer cartridge casing to rotated thegears as the assembly advances relative to the outer cartridge casing.Rotation of gears 716 and gear 718 can pivot the components of the upperand lower assembly so as to form the upper and lower supports,respectively.

FIGS. 19A and 19B schematically illustrate details of the self-expandingintervertebral joint assembly loaded in the cartridge as in FIGS. 17 and18, in accordance with embodiments of the present invention. Outercartridge casing 820 extends over at least a portion of intervertebraljoint assembly to permit advancement of the joint assembly into at leasta portion of the intervertebral space while the joint assembly issubstantially covered with outer cartridge casing 820. Outer cartridgecasing 820 covers pyramidal anchors 712 and pyramidal anchors 714.Distal component 720 of upper support 702 and distal component 730 oflower support 704 are located near an opening in outer cartridge casing820. Inner cartridge part 830 includes a wedge 832, upper flange 836 andlower flange 838. The upper and lower flanges include inner opposingsurfaces, and the inner surface of each flange opposes one of the wedgesurfaces to clamp the components of the upper and lower supports in aparallel configuration Inner cartridge part 830 is connected to shaft840.

Self expanding intervertebral joint assembly 700 includes structure topermit articulation between upper support 702 and lower support 704 torestore motion between the vertebrae. Upper support 702 has a protrudingstructure 725 which extends from middle component 724 and has a concavesurface feature formed therein, as shown herein above, which mates theupper surface of biconvex core 706. Lower support 704 has a protrudingstructure 735 which extends from middle component 734 and has a concavesurface feature formed therein, as shown herein above, which mates thelower surface of biconvex core 706. In an alternate embodiment, thefeatures of the upper and lower support are in direct contact and mateto provide articulation. For example, the upper support can have aprotrusion with a convex surface, and the lower support can have aprotrusion with a concave surface, in which the two surfaces mate toform a load bearing articulate joint.

Protruding structure 725 and protruding structure 735 can also includestructures to retain the biconvex core and upper and lower retentionring gears, respectively. Protruding structure 725 can include aretention ring, rim or annular flange as described above such as anannular flange 770 that projects radially inward toward biconvex core706 to retain biconvex core 706 Annular flange 770 has a bevel 772formed thereon to limit motion between the upper and lower supports.Retention ring gear 716 can have an annular shape formed to mate withprotruding structure 725. Protruding structure 725 can include an outercircular surface that mates with an inner surface of inner annularsurface of retention ring gear 716. Retention ring gear 716 can rotatearound protruding structure 725. In addition to inwardly protrudingannular flange 770 that retains biconvex core 706, protruding structure725 can include a retention element 774 such as an outwardly protrudingannular flange and/or C-ring clip to retain retention ring gear 716.Protruding structure 735 can include a radially inwardly projectingretention ring, rim or annular flange such as an annular flange 771 thatextends toward biconvex core 706 to retain biconvex core 706. Retentionring gear 718 can also have an annular shape formed to mate withprotruding structure 735. Protruding structure 735 can include an outercircular surface that mates with an inner annular surface of retentionring gear 718. Retention ring gear 718 can rotate around protrudingstructure 735. In addition to an inwardly protruding annular flange thatretains biconvex core 706, protruding structure 735 can include anoutwardly protruding retention element 775 such as an annular flangeand/or C-ring clip to retain retention ring gear 718.

Implant 700 includes structures that pivot while the upper and lowersupports are formed. A pivot gear 727 can engage upper retention ringgear 716. Pivot gear 727 is connected to joint 726 so that rotation ofpivot gear 727 rotates pivot joint 726 to rotate distal component 720. Apivot joint 728 connects proximal component 722 to middle component 724of upper support 702. Rotation about pivot joint 728 pivots middlecomponent 724 toward the deployed position. A pivot gear 737 can engagelower retention ring gear 718. Pivot gear 737 is connected to pivotjoint 736 so that rotation of pivot gear 737 rotates pivot joint 736 torotate distal component 704 toward the deployed position. A pivot joint738 connects proximal component 732 to middle component 734 of lowersupport 704. Rotation about pivot joint 738 pivots middle component 734toward the deployed position.

Wedge 832, upper flange 836 and lower flange 838 restrain motion of thejoint assembly during deployment by clamping the joint assembly whilethe joint assembly is advanced. Wedge 832 is positioned between uppersupport 702 and lower support 704. Wedge 832 and upper flange 836 engageproximal component 722 of upper support 702. Wedge 832 and lower flange838 engage proximal component 732 of lower support 704. Advancement ofinner cartridge part 830 advances wedge 832, upper, the upper and lowersupports distally to engage gears of the support

FIGS. 20A to 20E show a method for introducing the joint assembly withthe cartridge as in FIGS. 17 to 19 into an intervertebral space, inaccordance with embodiments of the present invention. The upper andlower supports are arranged and introduced together, although the upperand lower supports can be arranged sequentially. In a preferredembodiment, placement instrument 800 removably attaches to thecomponents and holds the components of the upper and lower supporttogether during assembly of the components as shown in FIGS. 20A-20D.The components of the upper and lower supports are arranged in a narrowprofile configuration while positioned within the cartridge. Thecomponents of each support can be arranged to a second wide profileconfiguration to form the assembled upper and lower supports.

Referring now to FIG. 20A, distal component 720 and proximal component722 of upper support 702 can be arranged in an elongate configurationfor introduction to the surgical site. Middle component 724 is foldedwithin a recess so that the upper support components have a slenderprofile for introduction into the surgical site. Distal component 730and proximal component 732 of lower support 704 are similarly arrangedin an elongate configuration, and middle component 724 is folded withina recess so that the lower support components have a slender profile.Outer cartridge casing 820 has an inner surface that includes astructure, for example a rack 824, formed thereon. Rack 824 includesteeth that can engage retention ring gear 716 and retention ring gear718. In alternate embodiments, the cartridge can comprise a gear on ornear the outer casing to engage at least one of the gears of thesupports. A joint 834 connects shaft 840 to inner cartridge part 830 andpermits shaft 840 to rotate while inner cartridge part 830 is advanceddistally. An arrow 754 indicates distal advancement of inner cartridgepart 830 and the components of the upper and lower supports in relationto rack 824 of outer cartridge casing 820. Rack 824 may not engage theretention ring gears until inner cartridge part 830 and the componentsof the upper and lower supports have advanced distally by apredetermined amount.

Referring now to FIG. 20B, inner cartridge part 830 has advanced thecomponents of the upper and lower supports a sufficient distance so thatrack 824 engages retention ring 824 of the upper support and theretention ring of the lower support. Retention ring gear 716 alsoengages pivot gear 727. Pivot gear 727 can be fixedly connected todistal component 720 of upper support 702 so that rotation of pivot gear727 pivots distal component 720. Rack 824 can also engage retention ringgear 718 of lower support 704. Pivot gear 737 of lower support 704 canbe fixedly connected to distal component 730 of lower support 704 sothat rotation of pivot gear 737 pivots distal component 730. Theretention ring gears can rotate about an axis of rotation that may beconcentric with the protruding structures that retain the biconvex core.The pivot gears can rotate about an axis of rotation that is concentricwith the pivot gears. In many embodiments, the axis of rotation of eachretention ring gear is aligned with the axes of rotation of each pivotgear so that the axes are parallel. The axis of rotation of pivot gear727 is concentric with an axis of rotation of joint 726, and the axis ofrotation of pivot gear 737 is concentric with an axis of rotation ofjoint 736.

Referring now to FIG. 20C, the components are shown in an intermediateconfiguration. Distal component 720 and distal component 730 pivotproximally with respect to the proximal components as indicated with anarrow 756. Distal component 720 pivots about joint 726, and distalcomponent 730 pivots about joint 736. Distal component 720 pivots to astop against proximal component 722. Retention ring gear 725, pivot gear727 and rack 824 are dimensioned to pivot distal component 702 apre-determined amount, for example 90 degrees, in response to retentionring gear 716 moving along rack 824. A pinion gear 750 engages rack 824while distal component 720 is positioned in the final deployedconfiguration. Pinion gear 750 can be mounted on proximal component 722and/or inner cartridge part 830. Distal advancement of inner cartridgepart 830 causes pinion gear 750 to engage rack 824 and rotate whileinner cartridge part 830 advances distally. Pinion gear can 830 engagepivot gear 729 and rotate pivot gear 729. Pivot gear 729 can be fixedlyconnected to middle component 724 so that rotation of pivot gear 729about joint 728 pivots middle component 724. Each of the components ofthe lower support can be similarly dimensioned and positioned to effectpivotal rotation of the lower components.

Middle component 724 can include a protrusion 760. Protrusion 760 can beshaped to slide within a channel 762, groove, or curved slot, formed indistal component 702. Pivotal rotation of middle component 724 canadvance protrusion 760 along channel 762. The components of the lowersupport can include a similar protrusion and channel.

Referring now to FIG. 20D, middle component 324 and middle component 334of the upper and lower supports, respectively, pivot outward after thedistal components are arranged. Stops can be provided on each of thedistal and middle components to limit pivoting motion of the middlecomponents about the proximal components. An arrow 758 indicates pivotalmotion of middle component 724 toward the final position to form theupper support. The upper and lower support can be fully formed once themiddle components pivot to reach the stops. Channel 762 includes an endthat receives protrusion 760 to stop pivotal motion of middle component724. Pinion gear 750, pivot gear 729 and channel 760 can be dimensionedso that pinion gear 750 reaches a distal end of rack 824 when protrusion760 reaches end 764 of channel 762. Pivot gear 729 rotates about an axisof rotation that can be concentric with a corresponding pivot gear onthe lower support 704. Joint 728 rotates about an axis of rotation thatcan be concentric with pivot gear 729.

Referring now to FIG. 20E, this isometric view shows middle component724 and middle component 734 in final positions, such that the upper andlower supports are fully formed. Screws 742, 744, 746 and 748 can beused to anchor the upper support and the lower to the superior andinferior vertebrae, respectively. In some embodiments, the outercartridge casing is inserted at least partially into and or near theintervertebral space while the upper and lower support components areadvanced relative to the outer cartridge casing and into theintervertebral space so as to form the upper and lower supports in theintervertebral space, for example as is shown in FIGS. 15A to 15D. Inmany embodiments, the upper and lower supports can be formed near theintervertebral space while the outer cartridge casing is positionedoutside and near the intervertebral space. In an embodiment, the jointassembly can be inserted partially into the intervertebral space in arigid wedge configuration and then allowed to freely articulate, so asto limit stretching and promote ligamentotaxis, as described inco-pending U.S. Appl. No. 10/913,780, filed Aug. 6, 2004, entitled“Methods and Apparatus for Invertebral Disc Prosthesis Insertion”, thefull disclosure of which has been previously incorporated herein byreference.

The prosthesis as shown in FIG. 20E with fully formed supports and amobile bearing core member disposed between the supports is capable ofseveral kinds of articulate motion. For example, flexion/extensionarticulate motion in the anterior and posterior directions, and lateralbending comprising side to side motion on the patient. The prosthesiscan also provide axial rotation between the supports, for examplerotation about a vertical axis of rotation, that corresponds to a twistalong the spine of the patient. The prosthesis can also providetranslation between the endplates with the mobile bearing core.

In many embodiments, the angles and lengths of the screws are selectedto provide safety. In specific embodiments, the screws are selected andangled to leave bone stock and process substantially intact.

In many embodiments the surfaces of the supports of prosthesis areadapted to anchor the prosthesis to the vertebrae. As can be seen withreference to the above figures, pyramidal anchors disposed in rows canbe located on the surfaces of the support components that engage thevertebrae. Such pyramidal anchors can be formed by machining thesurfaces to form a serrated surface. The expanded prosthesis can becoated to promote anchoring. In many embodiments, the bone contactingsurfaces of the upper and lower supports are coated with a bone growthpromoting substance. Examples include Titanium plasma spray coating,hydroxy apatite. In specific embodiments, the bone contacting surfacescan be coated with nano Calcium Phosphate particles to promote bonegrowth.

The upper and lower supports can comprise many biocompatible materials.In some embodiments the upper and lower supports comprise ceramic,ceramic composite, polymer, cobalt chrome, titanium and combinationsthereof.

FIGS. 21A to 21D show posterior and/or posterior lateral access to theintervertebral space, according to embodiments of the present invention.Embodiments provide in situ disc expansion within the disc space toprovide minimal disruption to the posterior bone support, facets andnerves and to retain the anatomical structures. In many embodiments, twofar posterio-lateral minimally invasive approaches are used so as toallow for the minimum of facet (zygophyseal) joint removal such that thefacet joints remain substantially intact. In many embodiments a TotalDisc Replacement (TDR) is provided.

An anterior aspect of the lumbar spine is shown in FIG. 21B. A posterioraspect 800 of the lumbar spine includes several spinal processes asshown in FIG. 8A. A disc 820 includes an annulus 822 and a nucleus 823.In many embodiments, these processes are remain substantially intactfollowing posterior and posterior-lateral insertion of theintervertebral prosthesis. In some embodiments, a naturally occurringand pre-existing opening 810 is used to access disc 820 posteriorly. Asuitably sized instrument, for example about a 9 mm diameter sizeinstrument, can be introduced into the naturally occurringintervertebral space through opening 810. In specific embodiments, theupper and lower supports each comprise about a 9 mm narrow profileconfiguration to pass through pre-existing opening 810. In someembodiments, an opening 812 can be formed to access the intervertebralspace, for example as shown in FIGS. 21A and 21D. An instrument with anarrow profile size of about 13 mm across may be used with suchopenings. Opening 810 can comprise cuts formed the inferior articularspinal process and/or cuts formed in the superior spinal process thatcomprise the facet joint, or zygophyseal joint, of adjacent spinalvertebrae. In some embodiments, the opening may be formed in a mannersimilar to that which is performed with Transforaminal Interbody Fusion(TLIF). In many embodiments, symmetric opposing openings are used toaccess the intervertebral space, for example pre-existing openingsand/or formed openings. In many embodiments, a posterior lateralapproach through soft tissue, for example a Wiltse approach is used toaccess the posterior aspect of the spine. A superior view of a lumbarvertebra is shown in FIG. 21C. In many embodiments, at least a portionof the surgical instruments and/or the expandable articulate prosthesiswill pass through the vertebral foramen, for example a foramen as shownin FIG. 21C. As the expandable articulate prosthesis may pass at leastpartially through the foramen, embodiments of the present invention maybe referred to as Transforaminal Interbody Articulation (TLIA, or TIA).A posterior lateral approach 832 permits access to disc 820 through thevertebral foramen.

In some embodiments it may be desirable to access the disc andintervertebral space with an anterior or anterior lateral approach usingthe expandable articulate prosthesis. With an anterior approach theexpandable prosthesis can minimize movement or disruption of the bloodvessels in front of the spine (descending aorta and vena cava), minimizethe formation of scar tissue during healing following device placementby reducing invasiveness of the anterior placement, avoid abnormalposterior anatomy would make an anterior approach more appropriate forthe patient (e.g. unusual nerve location).

FIGS. 22A to 22E show a method for introducing a joint assembly into anintervertebral disc space, in accordance with embodiments of the presentinvention. Annulus 822 of disc 820 is thicker anteriorly thanposteriorly. A first opening 920A is formed in a posterior portion ofannulus 822 with penetration of the annulus into nucleus 823 of disc820. A second opening 920B is formed in a posterior portion of annulus822 with penetration of the annulus into nucleus 823. A tissue removalinstrument 930 is inserted through opening 920A into nucleus 823 toremove nucleus 823. A viewing instrument 932, comprising an endoscope,arthroscope, fiber optic or the like, is inserted into opening 920B topermit viewing of the removal of nucleus 823. In some embodiments, theinstruments can be switched following removal of some tissue tofacilitated complete removal of the nucleus, for example viewinginstrument 932 inserted into opening 920A and tissue removal instrument930 inserted into opening 920B. Bilateral disc entry as shown canfacilitate disc decompression, insertion of the expandable prosthesis,and anchoring of the prosthetic disc.

An expandable member template 934B can be inserted into the evacuateddisc space through opening 92A with instrument 934 to determine thatsufficient tissue has been removed. Expandable member template 934B maycomprise an expandable balloon that can be filled with a radiopaquematerial. The balloon may comprise a radiopaque material, and beinflated with a gas and/or saline and the like. In specific embodiments,a Mylar balloon is filled with Barium solution and the Mylar Balloon hasan expanded shape that corresponds to the foot print of the expandablearticulate prosthesis. After viewing the shape of the expanded member,for example with fluoroscopy, additional tissue may be removed ifdesired. In some embodiments, the template may have radiographic markersto indict the midline and anterior/posterior orientation. A fluoroscopicimage of the template can be saved and compared to the prosthetic discimage. In many embodiments, the template has a lower height than theprosthesis that is sufficient to evaluate the footprint of materialremoved and ensure that sufficient material has been removed to allowexpansion of the prosthetic disc.

In some embodiments, a portion of the annulus may be removed to guidethe expandable prosthesis during delivery into the intervertebral space.The annulus comprises Type II collagen, which is strong, and can guideplacement of the prosthesis in some embodiments. In specificembodiments, the annulus can be shaped during the discectomy to guidethe prosthesis during deployment into the evacuated space, and theexpandable articulate prosthesis may be press fit anteriorly into theannular annulus so as to resist rotation within the disc space. Inspecific embodiments, the interior shape of the annulus formed duringdiscectomy corresponds to structures on the expandable articulateprosthesis, for example a foot print of the expandable articulateprosthesis.

An expandable articulate prosthesis 942 can be deployed with adeployment instrument 940 inserted through opening 920A. Deploymentinstrument 940 may comprise racks, gears, pulleys, cables and the likeas described above to expand prosthesis 942 as the prosthesis isadvanced into the disc space. A distractor 950 can be inserted throughopening 920B to distract the adjacent vertebrae while prosthesis isdeployed with expansion into the evacuated disc space. An instrument 960can be inserted into opening 920A to adjust the location of expandableintervertebral prosthesis 942 after the upper and lower supports arefully formed. Adjustment to the location of the disc with fully formedsupports can be done while distractor 950 is inserted through opening920B. Alignment can be accomplished using natural indicia such as thepedicles and/or with radiopaque markers, for example markers on theprosthesis. Screws can be passed through opening 920A to anchor theupper and lower supports on one side of the prosthesis, and screws canbe passed through opening 920B to anchor the upper and lower supports onthe other side of the prosthesis.

FIGS. 23A and 23B show radiopaque markers on upper and lower supports ofan expandable intervertebral prosthesis, according to embodiments of thepresent invention. FIG. 23A shows a superior view of an upper expandablesupport 1010 that comprises radiopaque markers 1012 positioned on theupper support. FIG. 23B shows an inferior view of a lower expandablesupport 1020 that comprises radiopaque markers 1012 positioned on thelower support. The radio opaque markers can be used to detect alignmentof the upper support and lower support in a manner similar to thatdescribed in U.S. application Ser. No. 11/187,733, filed Jul. 21, 2005,entitled “Intervertebral Prosthesis Placement Instrument”; U.S.application Ser. No. 10/903,913, filed Jul. 30, 2004, entitled“Intervertebral Prosthetic Disc with Metallic Core”, U.S. Publ. No.2006/0025862, the full disclosure of which has been previouslyincorporated by reference. The markers can be helpful in detectinganterior posterior alignment with fluoroscopy, lateral alignment withthe pedicles and rotation of the upper and/or lower support in relationto the pedicles. The markers can be used in addition to other indicia,for example with the pedicles to ensure that the posterior lateral edgesof the inserted disc are equidistant from the center of the pedicles andat the same disc level.

FIGS. 24A to 24E show a method of removing an expandable intervertebralprosthesis as in FIGS. 20A to 20E, in accordance with embodiments of thepresent invention. Screws 742, 744, 746 and 748 can be removed. Aninstrument with a casing as described above is introduced into theintervertebral space. The instrument comprises a distal end 1100 with anupper protrusion structure 1110 to engage the upper support through thescrew hole for screw 744 and a lower protrusion structure 1120 to engagethe lower support through the screw hole for screw 748, for example asshown in FIG. 24A. Other engagement structures on the supports andinstrument may be used. Outer cartridge casing 820 is advanced such thatpinion gear 750 is engaged with rack 824, for example as shown in FIG.24B. The implant may also be retracted while engaged with the protrusionstructures such that the rack and pinion gear are engaged. Thisengagement causes middle component 724 to swing under the proximalcomponent in a narrow profile configuration, for example as shown inFIG. 24C. Further retraction of the prosthesis and/or advancement of thecasing engages retention ring gear 716 with rack 824 so as to pivot thedistal component into the elongate and narrow profile configuration asshown in FIG. 24D. Retraction of the expandable intervertebral can becontinued so as to retract and fully collapse the prosthesis to thenarrow profile configuration as shown in FIG. 24E.

FIGS. 25A to 25D show blunt dissection of tissue to access theintervertebral space, according to embodiments of the present invention.A dilator 1210, for example a 20 gauge needle, is passed through a skin1220 of the patient to a posterior aspect 1230 of the spine of thepatient. Sequential dilators 1240 comprising blunt dissectioninstruments are sequentially passed over dilator 1210 and each otheruntil the tissue is dilated to a desired size. An operative tube 1250 isplace over the sequential dilators to provide access to posterior aspect1230 of the spine. Operative tube 1250 can be locked in place with anarm 1260. The dilators can then be removed to establish an operativecorridor. A posterior lateral approach can be made though muscle tissuein a minimally invasive fashion. Many of the other approaches describedabove can be made in a similar minimally invasive fashion with bluntdissection.

FIG. 26 shows an expandable intervertebral prosthesis 1300 comprising anupper support that engages a lower support to articulate, according toembodiments of the present invention. Upper support 1310 comprises anexpandable support as described above. Lower support 1320 comprises anexpandable support as described above. Lower support 1320 comprises aconvex protrusion 1322 to engage upper support 1310. Upper support 1310comprises a concave recessed surface 1312 to receive convex protrusion1322. Convex protrusion 1322 and concave recessed surface 1322articulate the upper and lower supports. The upper and lower supportscan articulate with at least one of a flexion/extension, a lateralbending or an axial rotation.

Referring now to FIG. 27, self expanding prostheses can be stacked inadjacent intervertebral spaces, according to embodiments of the presentinvention. A stacked arrangement 1400 comprises intervertebralprostheses in adjacent intervertebral spaces. Adjacent intervertebralspaces 1410 are defined by an upper vertebra 1402, a middle vertebra1404 and a lower vertebra 1406. In many embodiments, the prosthesiscomprises anchors adapted to permit stacking with another prosthesispositioned in an adjacent intervertebral space. An upper prosthesis 1420comprises upper anchors 1428 and lower anchors 1426. Upper prosthesis1420 comprises an expandable upper and lower support with a mobilebearing core member 1422 located between the upper and lower expandablesupports as described above. A lower prosthesis 1430 comprises upperanchors 1438 and lower anchors 1436. Lower prosthesis 1430 comprises anexpandable upper and lower support with a mobile bearing core member1432 located between the upper and lower support as described above. Theangles of the screws and/or other anchors may be oriented and positionedwith lengths to permit stacking of multiple prostheses in adjacentintervertebral spaces as described in U.S. Appl. No. 60/820,769, filedon Jul. 28, 2006, entitled “Spinal Prosthesis with Offset Anchors”, thefull disclosure of which has been previously incorporated by reference.Lower anchors 1426 of upper prosthesis 1420 are oriented outward andupper anchors 1438 of lower prosthesis 1430 are oriented inward, suchthat the tips of the anchors from each of the prostheses avoid eachother. In a specific embodiment a first expandable articulate prosthesisis placed with a posterior and/or posterior lateral approach in theintervertebral space defined by L4 and L5 and a second expandablearticulate prosthesis is placed with a posterior/posterior lateralapproach in the intervertebral space defined by L3 and L4.

FIGS. 27A to 27C show in situ deployment of an expandable articulateintervertebral prosthesis 1510 in an intervertebral space with aplacement instrument and a contralateral placement instrument, accordingto embodiments of the present invention. An inferior vertebra 1500comprises spinal processes as shown above. Two posterior lateral accessports can be formed with blunt dissection with a Wiltse approach asdescribed above. In many embodiments, the annulus remains substantiallyintact following removal of the nucleus, and the prosthesis ispositioned within the annulus via posterior lateral access openings inthe annulus as described above. A placement instrument 1520 is used toadvance prosthesis 1510 and a contralateral placement instrument 1530can be used to manipulate the prosthesis 1510 during deployment.Placement instrument 1520 can be attached to prosthesis 1510 with athreaded spacer 1524 that is positioned between the upper and lowersupports.

Prosthesis 1510 can comprise an elongate narrow profile configurationand an expanded wide profile configuration as described above and can beadvanced into the intervertebral space in the elongate narrow profileconfiguration. Prosthesis 1510 comprises upper and lower supports, andeach support can comprise a distal support component, a proximal supportcomponent and a middle support component as described above. A distalcomponent 1512 is pivotally connected to a proximal component 1516.While the components are advanced into the intervertebral space, distalcomponent 1512 pivots in relation to proximal component 1516. Inspecific embodiments, distal component 1512 is a final position whenpivoted to 90 degrees. A threaded leading edge spacer 1513, or distalspacer, can be attached to distal component 1512 to connect the distalcomponent to contralateral placement instrument 1530 with rotation ofthe contralateral placement instrument. A threaded trailing edge spacer1518, or proximal spacer, can be attached to proximal component 1516 toconnect the proximal component with placement instrument 1520 withrotation of the placement instrument. A middle component 1514 can pivotinto position after the distal component has pivoted into position asdescribed above.

A gut, or cable 1532 can be used to expand prosthesis 1510. Cable 1532can comprise, nylon or other suitable material, for example surgicalsuture material. Following preparation of the intervertebral space, forexample after a discectomy, cable 1532 can be threaded, or advanced,into one surgical access port, through the prepared intervertebral spaceand/or openings in the annulus, and out the other surgical access port.Tension in a proximal direction can be applied to cable 1532 to expandprosthesis 1510. Contralateral placement instrument 1532 comprises anopening to receive cable 1532 such that contralateral placementinstrument 1532 can be advanced distally to engage distal component1512. Cable 1532 can guide the contralateral placement instrument intoposition as the contralateral placement instrument is advanced distallyso as to engage the leading edge threaded spacer. The leading edgethreaded spacer can be positioned between the distal components andattached to the distal components with a cable. Threaded connection ofthe contralateral placement instrument to the leading edge spacerconnects contralateral placement instrument 1530 to distal component1512. Tension applied to cable 1532 can pivot distal component 1512 intothe deployed position. Additional displacement of cable 1532 can pivotmiddle component 1514 into position.

In many embodiments, the fully formed upper and lower supports can belocked into position with a locking mechanism. The locking mechanism maycomprise an insertable elongate member, a cam and/or a ratchet.Channels, or longitudinal slots, can be formed in the components toreceive an elongate member after the supports are fully formed, forexample a rod. The longitudinal slots can extend substantially along thelength of the respective component, for example along the length of theproximal component and/or along the length of the distal component. Inmany embodiments, the middle component swings clear of the channels whenpivoted into position, such that the elongate member can be insertedinto the slot while the middle component is in the deployed wide profileposition. Interference of the elongate member with the middle componentand/or proximal and distal components locks the components into positionwhile the support is fully formed. The elongate member may comprise anoval rod, a rectangular rod, and/or a circular rod and the like. Therods can be removed to collapse and remove the prosthesis. In manyembodiments, the rods and disc components may comprise a ratchetmechanism which retains the elongate member in position in thelongitudinal slots after insertion. In some embodiments, a cam mechanismis provided that rotates into position so as to lock the components intoposition, for example upon rotation of the middle component to thedeployed wide profile configuration.

In many embodiments, the placement instrument and contralateralplacement instrument are both connected to the prosthesis, for examplesimultaneously connected to the prosthesis. This connection of bothplacement instruments can be used to manipulate the prosthesis intoposition. In specific embodiments, both instruments are simultaneouslyconnected to the articulate, expanded prosthesis while the upper andlower supports are in fully formed and locked positions as describedabove and the support positioned in the intervertebral space and/orannulus.

FIGS. 28A to 28D show a placement instrument 1600 as in FIGS. 27A to27C, according to embodiments of the present invention. The placementinstrument can be inserted posteriorly through the canal and/or foramenso as to engage the boney endplates near the disc space. In manyembodiments, the placement instrument is inserted after two minimallyinvasive Wiltse incisions and/or dissections and a discectomy that usesa posterior parallel distractor. Placement instrument 1600 comprises adistractor with a distractor tip 1630 that can be inserted at leastpartially into the intervertebral space. Instrument 1600 comprises astop to limit penetration of distractor tip 1630. Instrument 1600comprises handles 1610 to distract the adjacent vertebrae. Instrument1600 comprises a hinge 1620 that opens distractor tip 1630 upon inwardmotion of handles 1610.

Instrument 1600 is adapted to pass the prostheses in an elongate narrowprofile configuration into the intervertebral space. Distractor tip 1630comprises a channel 1640 with grooves 1642 formed therein. Channel 1640is dimensioned to pass the prosthesis in an elongate narrow profileconfiguration. Grooves 1642 are dimensioned and spaced to receiveanchors on the external surfaces of the support components, for examplepyramidal components as described above. In some embodiments, theanchors may comprise elongate pyramidal anchors and or elongate keels orflanges and the grooves adapted to pass the elongate anchors with thegroove aligned with the elongate anchor. In many embodiments, channel1640 is sized to distract the vertebrae with distractor tip 1630 whilethe elongate prosthesis slides down channel 1640. Near hinge 1620,channel 1640 can be sized to pass the prosthesis with a sliding fit.

Instrument 1600 comprises an insertion tool 1650 to advance theprosthesis along channel 1640 so as to advance the prosthesis into theintervertebral space. Insertion tool 1650 comprises a shaft 1654 and ahandle 1652. Handle 1652 is connected to shaft 1654. In many embodimentshandle 1652 comprises a grub screw, and handle 1652 and shaft 1654comprise strong materials such that handle 1652 can be hammered so as todrive the prosthesis distally into the intervertebral space and distractthe vertebrae with separation of distal tip 1630.

FIGS. 29A to 29D show a contralateral placement instrument 1700 as inFIGS. 27A to 27C, according to embodiments of the present invention. Inmany embodiments, the placement instrument engages the prosthesis with aleading edge spacer 1706, or distal spacer. The expandable articulateintervertebral prosthesis comprises an upper support 1702, or superiorendplate, and a lower support 1704, or lower endplate. Spacer 1706 canbe attached to the upper and lower supports, for example attached with acable that can be cut. Contralateral placement instrument 1700 comprisesan elongate shaft 1710. Elongate shaft 1710 comprises a channel 1712.Shaft 1710 comprises an opening 1718 that exposes and extends to channel1710. Shaft 1710 comprises a nipple portion near a distal end 1730 thatextends between upper support 1702 and lower support 1704 when theinsertion tool is connected to spacer 1706. Spacer 1706 limitsarticulate movement between the upper and lower supports duringdeployment. Spacer 1706 may be provided as a part or component of aprosthesis assembly for insertion of the prosthesis into theintervertebral space, and spacer 1706 may be connected to shaft 1710.

Shaft 1710 can be connected to the prosthesis upon connection to spacer1706. Shaft 1710 comprises threads 1714 that engage threads on spacer1706. In some embodiments, the threads may be positioned on the nipple.Shaft 1710 comprises a shoulder 1716 that engages a shoulder stop 1708that limits threaded advancement of shaft 17170. Distal end 1730includes channel 1712 such that the cable can be threaded through shaft1710 from distal end 1730 to proximal opening 1718. A sleeve 1720, ortube, can be provided that fits over shaft 1710.

In many embodiments, sleeve 1720 may guide shaft 1710. Sleeve 1720 maybe sized to fit within an access tube. In many embodiments, shaft 1710slides inside sleeve 1720, and shaft 1710 may comprise a flange 1719that slides within sleeve 1720. A channel 1724, or space, can beprovided inside sleeve 1720 that allows clearance for flange 1719 whilethe flange slides inside the sleeve. A screw retained end cap 1722 maybe provided on the end of sleeve 1720.

In many embodiments, the trailing edge spacer, or proximal spacer issubstantially similar to the trailing edge spacer, or proximal spacer,and the spacers are removably attached to the upper and lower supports.The leading edge spacer and trailing edge spacer can be factory mountedand tied to the upper and lower supports with cable that can be cut, forexample nylon gut cable. The elongate members, for example longitudinalrectangular rods, are inserted into their designated slots so as to cutthe cable and release the spacers from the supports. In suchembodiments, the expanded upper and lower supports can be positioned inthe intervertebral space and/or annulus before the upper and lowersupports are locked.

An upper channel 1740 and a lower channel 1742 are each adapted toreceive an elongate support member. An upper elongate member 1750 issized to pass through upper channel 1740 formed in at least onecomponent of the upper support. A lower elongate member 1752 is sized topass through lower channel 1742 formed in at least one component of thelower support. An upper attachment cable 1760 attaches spacer 1706 toupper support 1702. A lower attachment cable 1762 attaches spacer 1706to lower support 1704. The upper and lower elongate members eachcomprise a sharpened distal end portion to cut the respective attachmentcable. Upper elongate member 1750 comprises a sharpened distal endportion 1758 to cut upper attachment cable 1760.

While the exemplary embodiments have been described in some detail forclarity of understanding and by way of example, a variety of additionalmodifications, adaptations, and changes may be clear to those of skillin the art. Hence, the scope of the present invention is limited solelyby the appended claims.

What is claimed is:
 1. A method for assembling an intervertebral implantin situ, the method comprising: introducing an implantable member intoan intervertebral space from a posterior side thereof, while theimplantable member is in a narrow profile, wherein the implantablemember has a first segment, a second segment, and a third segment,wherein the first segment is coupled to the second segment with a firstpivot joint and the second segment is coupled to the third segment witha second pivot joint; and sequentially pivoting the first segment toform an acute angle with respect to the second segment then pivoting thethird segment to form an acute angle with respect to the second segmentsuch that each of the first, second, and third segments is not parallelwith the other segments and the three segments together form three sidesof a triangle to deploy the implantable member from the narrow profileto a wide profile.
 2. The method of claim 1, wherein the step ofsequentially pivoting is performed by an insertion instrument removablyattached to the implantable member and configured to sequentially pivotthe first and third segments with respect to the second segment afterinsertion of the implantable member into a body of a patient.
 3. Themethod of claim 2, further comprising removing the insertion instrumentfrom the implantable member when the implantable member is in the wideprofile.
 4. The method of claim 1, wherein the implantable member isinserted into the intervertebral space from an opening in a spinal discannulus posteriorly.
 5. The method of claim 1, wherein the sequentialpivoting of the first and third segments is limited by first and secondstops which limit the pivoting of the first and third segments.
 6. Themethod of claim 1, wherein the first, second and third segments areretained in the narrow profile by an insertion instrument while theimplantable member is inserted into the intervertebral space.
 7. Themethod of claim 1, wherein the implantable member is a posteriorartificial intervertebral disc introduced into the intervertebral spacefrom a posterior lateral approach.
 8. The method of claim 1, wherein thefirst pivot joint has a first pivot axis extending through the firstsegment and the second segment and the second pivot joint has a secondpivot axis extending through the second segment and the third segment.9. The method of claim 8, wherein the first pivot joint comprises afirst aperture, the first pivot axis extending through the firstaperture and wherein the second pivot joint comprises a second aperture,the second pivot axis extending through the second aperture.
 10. Themethod of claim 8, wherein each of the segments has a first surfaceshaped to contact a first vertebra and a second surface shaped tocontact a second vertebra and wherein the first and second pivot axesextend through the first and second vertebrae when the first surfacecontacts the first vertebra and the second surface contacts the secondvertebra.
 11. The method of claim 10, wherein the first segment hasfirst pyramidal anchors and the second segment has second pyramidalanchors and the third segment has third pyramidal anchors and whereinthe first pivot axis extends between the first pyramidal anchors and thesecond pyramidal anchors and the second pivot axis extends between thesecond pyramidal anchors and the third pyramidal anchors.
 12. A methodof treating a patient having upper and lower vertebrae and anintervertebral space between the upper and lower vertebrae, the methodcomprising: providing an implantable assembly comprising a firstsegment, a second segment and a third segment, the first segmentpivotally connected to the second segment with a first pivot joint, thesecond segment connected to the third segment with a second pivot joint;introducing the first segment into intervertebral space when the firstsegment, the second segment and the third segment are arranged in anelongate configuration; pivoting the first segment about the first pivotjoint when the first segment is introduced into the intervertebralspace; and pivoting the third segment about the second pivot joint whenthe third segment is introduced into the intervertebral space, such thateach of the first, second, and third segments is not parallel with eachof the other segments so as to form a non-parallel arrangement, whereinthe first, second, and third segments form the three sides of a triangleso that the non-parallel arrangement is a triangular arrangement, andsuch that the implantable assembly supports the upper and lowervertebrae when placed in the intervertebral space.
 13. The method ofclaim 12 wherein the first pivot joint has a first pivot axis and thesecond pivot joint has a second pivot axis and wherein the first pivotaxis extends through the first segment and the second segment andwherein the second pivot axis extends through the second segment and thethird segment.
 14. The method of claim 13 wherein the first pivot axisand the second pivot axis extend along an inferior/superior orientationwith respect to the upper and lower vertebrae of the patient.
 15. Themethod of claim 14 wherein the first pivot axis and the second pivotaxis extend through the upper and lower vertebrae when the firstsegment, the second segment and the third segment are placed in theintervertebral space.